1. Field of the Invention
The present invention relates to a sealed battery pack in which a plurality of cells are disposed in series into an integrated battery case.
2. Description of the Related Art
A sealed battery pack of this type is disclosed in Japanese Laid-Open Patent Application H7-85847. As shown in FIG. 16, this sealed battery pack 61 is structured such that elements for electromotive force are housed in cases 63 formed in a bottomed, prismatic shape, the openings in the cases 63 are sealed with lids 64, a plurality of the resulting cells 62 are disposed in series, and the cases 63 of these cells 62 are bound together with end plates 65 and restricting bands 66. The positive electrode terminals 67 and negative electrode terminals 68 of the cells 62 protrude upward through the lids 64, and these terminals 67 and 68 are successively connected in series by an electrical connecting bar 69.
Japanese Laid-Open Patent Application H6-215804 discloses a mono-block rechargeable battery in which plastic cell cases and lids are welded, wherein a cooling jacket is provided between the side plates and the side walls of the cases by welding the side plates, which have recessed spaces formed on their insides, to the outer surfaces of the two opposing side walls of the cases, and cooling liquid inlet orifices and outlet orifices are provided to the upper part of the two ends of the side plates.
Japanese Laid-Open Patent Application S61-45571 discloses that cooling passages are provided above and below through the cell separators of a mono-block case, headers are provided above and below for allowing a coolant to flow in and out, and a separate lid is provided for every cell.
However, with the sealed battery pack of Japanese Laid-Open Patent Application H7-85847, because the cells were disposed in close contact and bound together, not enough heat was radiated away from the cells when the ambient temperature was high or when the battery was charged or discharged at a high current. This not only raised the battery temperature and shortened the battery service life, but could potentially lead to damage of the battery case if the temperature further rose up to the heat resistance temperature of the synthetic resin from which the battery case was made.
In contrast, with the rechargeable battery in Japanese Laid-Open Patent Application H6-215804, temperature increases could be suppressed to a certain extent because the sides of the cell case were cooled by the cooling jacket, but with a rechargeable battery comprising a group of cells as shown in FIG. 16, increases in the temperature of the cells could not be adequately controlled because there was no cooling between the cells. Also, since the cooling jacket was produced by welding side plates to the cell case, a rechargeable battery comprising a group of cells in particular entailed numerous welding steps and was therefore complicated, and another problem was ensuring a good seal for the coolant.
With the rechargeable battery in Japanese Laid-Open Patent Application S61-45571, the portion forming the cooling passages above and below in the cell separators in the mono-block case was forcibly cooled, but the cooling effect was inadequate because the entire outer surface of each cell was not forcibly cooled. The complexity of the case structure also drove up the manufacturing cost, and since a lid had to be provided for every cell, assembly took longer and added to the cost, among other problems.
The present invention was conceived in light of the above problems, and it is an object thereof to provide a sealed battery pack with which the cells can be effectively cooled with an inexpensive structure, and good sealing can be ensured with a simple sealing and joining process.
The sealed battery pack of the present invention comprises a plurality of serially disposed cells in which power generating elements are housed in bottomed, prismatic cell cases and the openings thereof are sealed, wherein the plurality of serially disposed cells are housed in a cooling box, the top openings in the cooling box and the openings in the various cell cases are sealed by an integrating lid, and coolant passages are formed by causing the various cell cases to communicate with each other between the sides of the cells and the inner walls on both sides of the cooling box in the direction in which the cells are disposed. Because all of the sides of the cells, including those between the cells, can be forcibly cooled with a coolant that flows through coolant passages, all of the cells can be effectively cooled and higher performance can be ensured. Also, because a plurality of serially disposed cells are housed within a cooling box, a coolant passage with a good seal can be formed merely by sealing the tops of the cells with an integrating lid, coolant passages can be formed with a simple sealing and joining process in just the vertical direction with a small number of parts, and a sealed battery pack with high reliability and performance can be obtained inexpensively with less assembly work.
The structure may also be such that the lid comprises a middle lid which is joined at the bottom to the upper ends of the cooling box and the various cell cases, consists of a ladder-like framework that separately partitions the openings in the various cell cases, and is provided with a connector for electrically connecting adjacent cells, and an outer lid joined to the top of the middle lid. In this case, a sealed battery pack can be easily manufactured by joining the middle lid to the tops of the cases and the cooling box and connecting the connectors and power generating elements of the various cells, and then joining the outer lid over this. A coolant passage can also be formed by joining the cases to the cooling box and the middle lid, which eliminates the need for sealing with respect to the coolant in the connector portion, and ensures a highly reliable electrical connection with a simple structure.
If the cell cases, lid, and cooling box are made of a synthetic resin and integrated by being joined together by welding, a rechargeable battery in which the cells are integrally grouped in a case can be manufactured with good productivity by simple welding in just the vertical direction.
If latching members are provided within the coolant passages between cell cases at a suitable distance in the cell disposition direction from the side walls of the cooling box on both sides in the cell disposition direction, and protrusions that engage with the latching members are provided to the side walls of the cell cases, the engagement of the protrusions and the latching members will prevent the displacement of the cooling box outside of the side walls. Even if the two side walls of the cooling box are not welded to the cell cases, there will be enough strength to prevent the side walls of the cooling box from being distended by the internal pressure of the coolant passages on both sides.
If the latching members are formed protruding upward from the corners of step-like partitions cut out in the shape of steps on both sides and leading upward, the latching members can be engaged without interfering with the protrusions disposed at a plurality of places above and below merely by inserting the serially disposed cells in the cooling box from above. Furthermore, the latching members can be provided by integrally molding the step-like partitions in the cooling box, and since the cooling box can be removed from the mold in a single direction, this structure affords easier molding and less expensive manufacture.